The objective of the 10th International Meeting of Chromosome 21 & Down Syndrome is to bring together investigators from the international community with a broad spectrum of research interests to discuss the current state of knowledge regarding Down syndrome and human chromosome 21. Topics for discussion are designed to encompass all relevant areas of biology, molecular biology, and medicine, including functional genomics and neurobiology. Invited speakers will present an overview highlighting topical issues. These introductions will be followed by platform presentations from submitted abstracts. The organizers anticipate a small but highly interactive meeting to facilitate the exchange of the latest ideas between senior and junior scientists, including postdoctoral fellows. Following the sequencing of chromosome 21, researchers are putting the results of these molecular analyses into biological context. This can best be done with a multidisciplinary group of researchers including those specializing in the mental retardation and cognitive deficits of Down syndrome, the neurobiology of Down syndrome, congenital heart defects, immune deficits, leukemia, craniofacial abnormalities, communicative and digestive disorders, and premature aging, as well as genomic research, transgenic mouse construction and analysis, and mouse behavioral studies. It is anticipated that this conference will foster interaction across disciplines, help to focus and redirect research efforts for maximal use of developing data, and establish new collaborations and avenues of investigation.